The practice of using so-called wavefront manipulators for correcting aberrations, e.g. in microlithographic projection lenses, is known. Such manipulators typically produce the wavefront correction by mechanical manipulation, for example by changing the position and/or producing a deformation of the element serving as a manipulator. However, mechanical manipulators typically can only correct low-order wavefront errors, while higher-order wavefront errors, as may be caused by a high thermal load on the optical elements, generally cannot be compensated sufficiently by mechanical manipulators. Therefore, for correcting higher-order wavefront errors, thermal actuators are used so as to change the optical properties of optical elements by a targeted, generally spatially resolved thermal manipulation.
For correcting an imaging property of a projection system in a projection exposure apparatus for the VUV wavelength range, U.S. Pat. No. 8,111,378 B2 proposes the application of radiation in a wavelength range which differs from a wavelength range of an exposure beam of the projection exposure apparatus to at least part of an optical element, typically a lens element, by way of a spatial waveguide mechanism.
WO 2012/013747 A1 discloses the practice of controlling the spatially dependent temperature distribution in a substrate of a reflective optical element with the aid of a heat-controlling device in two or three spatial directions. The heat-controlling device can comprise heating elements, for example in the form of ohmic heating elements, which can be arranged in a grid arrangement. It is also possible to provide radiation sources, which act on the substrate or on the reflective optical element by thermal radiation (e.g. IR radiation), as heating elements in order to thermally manipulate said substrate or said reflective optical element. In this case, an absorption layer serving to absorb the IR radiation can be arranged below a reflective surface of the optical element. Control parameters which are related to the temperature or the deformation of the optical element can be fed to a control device of the heat-controlling device such that the control device can be used to reduce the aberrations of the reflective optical element.
WO 2013/044936 A1 discloses the practice of arranging a wavefront correction device comprising a refractive optical element in a microlithographic projection lens. First and second heating radiation can be radiated onto a first and second portion, respectively, of a circumferential edge area of the refractive optical element, which heating radiation at least partly penetrates into the optical element. A refractive index distribution caused by the partial absorption of the heating radiation within the optical element serves to modify or at least partly correct a wavefront error.
PCT/EP2013/000728 proposes to arrange in a projection lens a wavefront correction device in the form of a mirror comprising a reflective coating and a mirror substrate. First and second heating radiation can be radiated into a first and second portion, respectively, of a circumferential edge area of the mirror substrate, which heating radiation at least partly penetrates into the mirror substrate. A temperature distribution in the substrate caused by the partial absorption of the heating radiation leads to a deformation of the mirror, which serves to modify or at least partly correct a wavefront error.
WO 2009/046955 A2 describes a device for controlling the temperature of an optical element which is provided in a vacuum atmosphere. The device comprises a cooling apparatus, which comprises a radiation-cooling part spaced apart from the optical element so as to cool the optical element by radiation with the aid of heat transfer. The device also comprises a control device for controlling the temperature of the radiation-cooling part and a heating part for heating the optical element, wherein the heating part is connected to the control device in order to control the temperature of the heating part.
WO 2009/152959 A1 describes a projection exposure apparatus for semiconductor lithography, which comprises a thermal manipulation device of an optical element comprising a front side for reflecting electromagnetic radiation and a rear side. Thermal actuators which act on the optical element from the rear side are present. The thermal actuators can be LEDs or lasers, the emission spectrum of which can lie in the IR wavelength range. Such thermal actuators can emit electromagnetic radiation which at least partly passes through the substrate and which is at least partly absorbed by an absorption layer arranged between the substrate and the multi-layer coating. The absorption layer can include a lacquer layer, a metal powder, aluminium or a glass and has a typical thickness of between 5 μm and 15 μm.